STAR-RISs: Simultaneous Transmitting and Reflecting Reconfigurable Intelligent Surfaces

TLDR

The letter studies simultaneous transmitting and reflecting reconfigurable intelligent surfaces (STAR‑RISs). STAR‑RISs extend coverage to 360° by simultaneously transmitting and reflecting, and the authors present a hardware model, near‑ and far‑field channel models, and analyze their diversity gain relative to conventional RISs. Numerical simulations verify analytical results and demonstrate that full diversity order can be achieved on both sides of the STAR‑RIS.

Abstract

In this letter, simultaneous transmitting and reflecting reconfigurable intelligent surfaces (STAR-RISs) are studied. Compared with the conventional reflecting-only RISs, the coverage of STAR-RISs is extended to 360 degrees via simultaneous transmission and reflection. A general hardware model for STAR-RISs is presented. Then, channel models are proposed for the near-field and the far-field scenarios, based on which the diversity gain of the STAR-RISs is analyzed and compared with that of the conventional RISs. Numerical simulations are provided to verify analytical results and to demonstrate that full diversity order can be achieved on both sides of the STAR-RIS.